This invention relates to a fossil-fired thermal system such as a power plant or steam generator, and, more particularly, to a method for continuously monitoring the thermal system at a location remote from the system, advising the system operator of corrections, improvements and warnings which improve system operations. Such advise may include diagnostic information, Dynamic Heat Rate and notice of tube failures.
Although especially applicable to xe2x80x9cInput/Loss methodsxe2x80x9d installed at coal-fired power plants, this invention is applicable to any other heat rate method installed at a thermal system for on-line monitoring; said method monitoring in a continuous manner (i.e., on-line) resulting in the determination of one or more of the following quantities: fuel flow, effluent flow, emission rates, fuel chemistry, fuel heating value, boiler efficiency, and/or system heat rate. Note that xe2x80x9cThe Input/Loss Methodxe2x80x9d and its associated technologies are described in the following U.S. patent applications Ser. No. 09/273,711 (hereinafter termed ""711), Ser. No. 09/630,853 (hereinafter termed ""853), Ser. No. 09/827,956 (hereinafter termed ""956), Ser. No. 09/759,061 (hereinafter termed ""061), Ser. No. 10/087,879 (hereinafter termed ""879), and Ser. No. 10/131,932 (hereinafter termed ""932); and in their related provisional patent applications and Continuation-In-Parts. One of several rudimentary Input/Loss methods is described in U.S. Pat. No. 5,367,470 issued Nov. 22, 1994 (hereinafter termed ""470), and in U.S. Pat. No. 5,790,420 issued Aug. 4, 1998 (hereinafter termed ""420).
The importance of accurately determining system heat rate is critical to any thermal system (heat rate being inversely related to system thermal efficiency, common units of measure being Btu/hour per kilowatt, or Btu/kWh). If practical hour-by-hour reductions in heat rate are to be made, and/or problems in thermally degraded equipment are to be found and corrected, then accuracy in determining system heat rate is a necessity as well as the quality of diagnostic information made available associated with degraded equipment. Any on-line monitoring method determining system heat rate must be properly maintained by the system""s engineering staff. However, de-regulation of the electric power industry and/or economic down-turns may result in reductions of such engineering staffs. Further, the expertise needed to solve all problems arising at a thermal system may not be immediately available to the local staff. Further, given complexities of most thermal systems, and especially large commercial power plants burning coal, the system operator must keep track of dozens of important parameters which might impact system heat rate. The system operator has had no single parameter which feedbacks in real-time the consequences of his/her latest adjustments made to the system.
The problem of coping with complex thermal systems, and especially large commercial power plants burning coal, has never been adequately been address by the industry. A system operator would desire to have feedback on individual equipment, given adjustments to that equipment, as to how it impacts system heat rate. For example: if hot reheat temperature is lowered by the operator, what is the impact on system heat rate? Solution to such problems includes developing differential heat rates (hrj) for individual equipment and processes (e.g,, hrReheat for the Reheater heat exchanger, hrComb for the combustion process, etc.). One attempt to provide such operator feedback, as established art, is the use of the xe2x80x9ccontrollable parametersxe2x80x9d method to determine differential heat rates. In this method, a few (typically less than a dozen) measured system parameters are monitored relative to a reference value (also termed a bogey value or targeted value). For a turbine cycle associated with a conventional power plant, controllable parameters include at least throttle pressure, throttle temperature, reheat temperature and condenser pressure. For the boiler, controllable parameters may include stack tempers, excess air and/or Air/Fuel ratio. One teaching, known to the inventor, of controlling the Air/Fuel ratio to gain improvement in boiler performance is U.S. Pat. No. 4,969,408 by DH Archer and M Ahmed, issued Nov. 13, 1990.
In general, to assure quality feedback to the operator, differential heat rates should sum to system heat rate: xcexa3hrj=HR; thus assuring that individual effects consistently impact the system as a whole. The problem is that current industrial practice, including the controllable parameters approach, computes differential heat rates in isolation. For example, the effects of changing hot reheat temperature is typically established by computer simulation of a turbine cycle, holding boiler efficiency constant, said effects then being assigned to the entire system. In like manner, boiler parameters are altered in computer simulators without consideration to effects on the turbine cycle. Even if such practices were applied to a system which maintains constant power output, burning uniform fuel environmental conditions alter with the seasons effecting such sensitivities. Coal-fired systems commonly operate with variable load and highly variable fuel quality. Indeed, use of such differential heat rates, computed in isolation, is the only known modality for on-line monitoring of thermal systems, with the exception of The Input/Loss Method. When the impacts of controllable parameters are computed in isolation, turbine cycle differential heat rates or boiler xcex94efficiencies have little value, offering no consistent feedback to the operator.
Whereas The Input/Loss Method, when employing the Fuel Consumption Index (FCI) technique, addresses a portion of the problem of determining differential heat rates; the FCI technique does not compute hrj values in isolation. The FCI technique, as establish art, computes differential heat rates based on principles founded in the Second Law of thermodynamics. The FCI technique forces system integration; hrj effects will always sum to system heat rate. However, a limiting requirement of the FCI technique is that it requires knowledge of the constituents of the As-Fired fuel, As-Fired fuel heating value, system mass balances (i.e., fuel, combustion gases and working fluid), and routine system xe2x80x9cOperating Parametersxe2x80x9d.
References for the Fuel Consumption Index technique include the following: F. D. Lang, and K. F. Horn, xe2x80x9cFuel Consumption Index for Proper Monitoring of Power Plantsxe2x80x9d, Proceedings of the 1991 Heat Rate Improvement Conference, Scottsdale, Ariz., sponsored by the Electric Power Research Institute, Palo Alto, Calif., May 7-9, 1991; also published as xe2x80x9cPractical Experience with Second Law Power Plant Monitoringxe2x80x9d in Energy for the Transition Age (Proceedings of the Florence World Energy Research Symposium, FLOWERS ""92, Jun. 7-12, 1992, Florence, Italy), Edited by Sergio S. Stecco, Nova Science Publishers, Inc., Commack, N.Y., 1992, pages 487-501, ISBN 1-56072-083-4; also published as xe2x80x9cPractical Experience with Second Law Power Plant Monitoringxe2x80x9d in Advances in Power Engineering (Proceedings of International Power Engineering Conference, May 17-21, 1992, Hangzhou, People""s Republic of China), Edited by Cen Kefa and David Y. S. Lou, International Academic Publishers, Beijing, China, 1992, pages 68-77, ISBN 7-80003-190-X/TK-17; also xe2x80x9cFuel Consumption Index for Proper Monitoring of Power Plantsxe2x80x9d is publically available, with updates through Revision 10 of Oct. 6, 1998, from Exergetic Systems, Inc., San Rafael, Calif. (note that this Revision 10 reflects all prior related technologies published elsewhere).
There is no known art related to this invention. There is, however, a clear need to improve the quality and consistency of information provided to operators of thermal systems, especially to those of coal-fired power plants, and to assist them in improving system heat rate.
This invention relates to a fossil-fired thermal system such as a power plant or steam generator, and, more particularly, to a method for continuously monitoring the thermal system at a location remote from the system, causing corrections, improvements and warnings of tube failures to be made by providing performance diagnostic information to the system operator including Dynamic Heat Rate.
This invention addresses the problems discussed by teaching remote monitoring techniques and through use of Dynamic Heat Rate, providing quality and consistent operator feedback for improving system heat rate. Although the general concept and use of system heat rate is common art in the electric power industry, having been in use since at least the 1930s, there is no known reference in the literature to the Dynamic Heat Rate concept. The works of ""470 and ""420 make no mention of Dynamic Heat Rate. Although the technologies of ""711, ""853, ""956, ""061, ""879 and ""932 support this invention, enhancing the quality of diagnostic information provided to the system operator, they make no mention of Dynamic Heat Rate, nor of remote diagnostics.
Given that the FCI technique requires knowledge of the constituents of the As-Fired fuel, As-Fired fuel heating value, system mass balances especially As-Fired fuel flow, and routine system Operating Parameters, to apply the FCI technique to systems in which such information is not directly available, this invention teaches to combine FCI techniques with Input/Loss methods and with continuous monitoring techniques, leading to quality and consistent operator feedback for improving system heat rate. In the preferred embodiment the FCI technique requires The Input/Loss Method as taught in ""711 and ""879, with high accuracy boiler efficiencies as taught in ""853, with general support found in ""956 and ""061, with tube failure detection methods taught in ""932; or equivalent Input/Loss methods.
However, actual applications of The Input/Loss Method at coal-fired systems as revealed that computed FCIs and system heat rates may produce considerable data scatter. This has been found true, at certain times, for systems burning low quality or variable quality coals; such coals include at least: sub-bituminous C, Powder River Basin coals, lignites and brown coals. For such systems this scatter may be significant enough to preclude useful information being presented, or otherwise absorbed, by the operator to act in an appropriate manner (FIG. 1 illustrates such scatter, discussed below). If the electric power industry is to burn fossil fuels more efficiently, thus reducing emission flows, which is especially sensitive at systems burning poor quality coal, then improvement is needed. Indeed, what is needed is a straightforward presentation of the effects an operator causes, which, as taught by this invention, is Dynamic Heat Rate.
This invention adds to the technology associated with Input/Loss methods. As taught in ""711, ""853, ""879 and ""932, The Input/Loss Method has been applied through computer software, installable on a personal or other computer termed a xe2x80x9cCalculational Enginexe2x80x9d, and has been demonstrated as being highly useful to power plant engineers. This invention teaches to connect the Calculational Engine with a personal or other computer termed a xe2x80x9cRemote Enginexe2x80x9d. The Remote Engine receives data from, and sends data to, the Calculational Engine. The Calculational Engine continuously determines system heat rate, Fuel Consumption Indices, differential heat rates based on Fuel Consumption Indices, Dynamic Heat Rate, and other thermal performance information in essentially xe2x80x9creal-timexe2x80x9d (on-line), as long as the thermal system is burning fuel. The Remote Engine, receiving such information, prepares appropriate diagnostic information which can be easily interpreted by the system operator when such information is sent back to the Calculational Engine. Such diagnostic information may consist of changes in correction factors associated with effluent measurements; such correction factors being taught in ""879. Such diagnostics information may consist of at least warnings to the system operator that his/her latest actions have a detrimental effect on system heat rate. Also, the Remote Engine may send diagnostic information related to tube failures to the system operator; such tube failure methods being taught by ""932. The application of this invention to The Input/Loss Method, installed as part of the Calculational Engine and the Remote Engine, significantly enhances the power plant operator""s ability to improve system heat rate.
It is therefore an important object of the present invention to teach how Dynamic Heat Rate is determined.
It is therefore a further object of the present invention, to demonstrate how Dynamic Heat Rate leading to consistent differential heat rates may be used to improve system heat rate.
It is therefore a further object of the present invention to teach how the Calculational Engine, producing Dynamic Heat Rate, tube failure warnings and diagnostics, and other thermal performance information, and the Remote Engine, communicate electronically.
Other objects and advantages of the present invention will become apparent when its general methods are considered in conjunction with the accompanying drawings and the related inventions of ""711, ""853, ""956, ""061, ""879 and ""932.